This invention relates to a process and apparatus for the recovery of one or more components of a raw gas, absorbed by the scrubbing liquid during a physical gas scrubbing step, by expanding the laden scrubbing liquid. (By laden or loaded scrubbing liquid is meant scrubbing liquid containing absorbed gaseous components.)
In a physical gas washing procedure, other components contained in the raw gas are dissolved in addition to the component to be scrubbed out, the amount of dissolved gas being proportional to the partial pressure and the solubility of the individual gases.
If these concomitantly dissolved components are desirable as constituents of the product gas, this phenomenon represents a not inconsiderable loss in yield, so that a recovery of these valuable components is advantageous.
A process for the recovery of such valuable components has been disclosed wherein the loaded scrubbing liquid is expanded and a thus-produced gaseous fraction, containing the largest portion of the concomitantly dissolved components and a partial quantity of the component to be scrubbed out, is re-mixed with the gas, after recompression to the raw gas pressure, while the liquid fraction is conducted to a further regenerating stage.
Such a process is applicable in many cases and is also economical. For example, if it is intended to scrub out acidic components, from a raw gas obtained from a plant for the partial oxidation of, for example, sulfur-containing crude oils, which raw gas contains, hydrogen, hydrogen sulfide, carbon dioxide, carbon monoxide, methane, and nitrogen, to obtain the hydrogen as a product gas, then, by means of a simple expansion in the described manner, such an amount of hydrogen can be recovered from the loaded scrubbing liquid that the hydrogen yield is above 99%. This is possible, because the relative solubilities of hydrogen to carbon dioxide is very high.
In contrast thereto, if it is desired that the product gas contain methane in addition to hydrogen, which is very advantageous if the product gas is to be employed as heating gas or as the starting product for synthetic natural gas, then the methane cannot be recovered sufficiently completely by a simple expansion, since the solubilities of methane and carbon dioxide are relatively close to each other. Moreover, a large portion of the dissolved carbon dioxide is degassed during the expansion, thereby requiring increased compression energy for the recompression of the gas, and simultaneously the amount of the carbon dioxide to be scrubbed out from the raw gas is also increased.
Therefore, this invention is based on the problem of developing a more efficient process and apparatus for the recovery of high yields of valuable components concomitantly dissolved in a scrubbing liquid.